Air infiltration, an important energy loss mechanism in buildings, has been studied in a number of tight homes in Sweden. Two methods of measurement have been used: the fan pressurization technique was used for measuring the airtightness of the building envelope and the tracer gas technique was used for measuring the natural and mechanical ventilation. An automated air infiltration measurement system was developed. The system works on the principle of keeping a constant concentration of a tracer gas. Pressurization is used routinely for checking dwellings in Sweden. This technique does not give the air infiltration as a direct result.

A previously developed model correlating airtightness and air infiltration was used for evaluating the performance of the tested houses. The original model was developed at Lawrence Berkeley Laboratory for American homes and has now been modified for Swedish homes.

The results show that it is difficult to model air infiltration, and that it is difficult to achieve the recommended minimum ventilation rate as given in the Swedish Building Code if you are to rely only on natural ventilation in a tight home. Most new Swedish homes meet the airtightness requirement of the Swedish Building Code and are equipped with mechanical ventilation.

The paper presents results from measurements in Swedish homes using the tracer gas technique and the pressurization technique. The techniques are described. The results from the measurements are compared with predictions using a model correlating airtightness and air infiltration.